Preheat oven to 220°C. Wash ducks inside and out under cold running water and pat dry with absorbent paper. Season to taste, place on a rack over a large roasting tray, and roast until starting to brown (20 minutes).

Combine potatoes, garlic and half the thyme in a large roasting tray, carefully spoon over hot duck fat from duck roasting tray (be careful as hot fat will spit), season to taste and stir to coat. Reduce oven to 180°C and roast duck and potatoes until duck is almost cooked through (25 minutes).

Carefully remove rack with ducks, set aside. Pour fat from duck roasting tray (discard, or strain and reserve for another use), then add cherries, malmsey, stock, orange rind, bay leaf and remaining thyme to duck roasting tray, season to taste, stir to combine, place ducks and rack back over cherries and roast until duck is cooked through (15-20 minutes; to test, pierce duck thigh with a skewer and juices should run clear). Remove duck, cover loosely with foil and set aside to rest (15-20 minutes). Roast cherry mixture until thick and reduced (10-12 minutes), transfer to a jug and keep warm. Remove potatoes and keep warm.